Conventionally, there is a widely known sealed battery including an electrode body and a case for housing the electrode body together with electrolyte solution, the electrode body formed by layering paired electrodes (positive and negative electrodes), which are formed into sheet shapes, with a separator sandwiched therebetween and by winding the electrodes and the separator.
In the above-mentioned sealed battery, the case is sealed by welding the case and a sealing member arranged to plug a pouring hole formed in the case after pouring the electrolyte solution into the case through the pouring hole.
In the sealed battery, the case needs to be completely sealed. When the sealing member and the case are welded together, the electrolyte solution attached to the pouring hole may cause welding faults.
A technique for solving such a problem is described in Patent Literature 1.
As shown in FIG. 7, a sealed battery described in Patent Literature 1 includes a case having a housing portion for housing an electrode body (not shown) and a lid portion for closing an open face of the housing portion. A recess which is recessed toward the inside of the case is formed in the lid portion and a pouring hole connecting the inside and the outside of the case is formed in the recess.
In the sealed battery described in Patent Literature 1, the case is sealed by fitting a rubber sealing plug into the pouring hole to thereby seal the pouring hole. Furthermore, the case is completely sealed by inserting a plate-shaped sealing plate, which is fixed to a portion (upper portion in FIG. 7) of the sealing plug on an opposite side from the fitted portion, into the recess and by joining the sealing plate to the case by laser welding.
In this manner, by sealing the pouring hole, to which electrolyte solution may be attached, with the sealing plug and then by joining; the sealing plate to the case by the laser welding, the ease is reliably sealed and welding faults are reduced.
However, in the sealed battery described in Patent Literature 1, a minute space is defined by the recess in the lid portion, the sealing plug, and the sealing plate. Therefore, when the sealing plate and the case are joined together by the laser welding to seal the space, gas which is present in the space may rapidly expand due to heat of a laser beam, and melted portions of the sealing plate and the case may flow outside the case to thereby cause the welding faults.